1. Field of the Invention
The present invention relates to a fuel cells stack which uses a polymer electrolyte membrane type fuel cell employing a hydrogen as a fuel and employing an air as an oxidizing agent.
2. Description of the Prior Art
A polymer electrolyte membrane type fuel cell uses an ion exchange membrane corresponding to a fixed polymer electrolyte for an electrolyte, a generally schematic view thereof is shown in FIG. 6. In this structure using the ion exchange membrane 20, a fuel cell 23 corresponding to a unit battery is constituted by forming a positive pole 21 and a negative pole 22 in a layered shape on both surfaces of the ion exchange membrane 20 and combining them. In the case of employing a hydrogen as a fuel, in the negative pole, the following reaction is affected on a contact interface between the catalyst and the polymer electrolyte.
H2xe2x86x922H++2exe2x88x92
Further, in the case of employing an oxygen as the oxidizing agent, in the positive pole, the following reaction is affected, so that a water is produced.
1/202+2H+2exe2x88x92xe2x86x92H2O
The catalyst corresponds to an activating point for the reaction, the electrode layer corresponds to a transmitting body for an electron in the reaction, and the polymer electrolyte corresponds to a transmitting body for a hydrogen ion. The fuel cell 23 is structured as shown in FIG. 7 such that a fuel gas flow passage is formed on one side surface and an oxidizing agent gas flow passage is formed on the other side surface, and a lamination of each of the fuel cells is performed by being connected in series with using a separator plate 24 having the fuel gas flow passage and the oxidizing agent gas flow passage for supplying the fuel gas and the oxidizing agent gas and the cooling water flow passage for cooling the fuel cells stack, and a gasket 25, forming a laminated body 26 as shown in FIG. 8 so as to form a fuel cells stack and fastening by an end plate 27, thereby forming one power generating unit.
The fuel cells itself constituted in this manner becomes a heat generating source since an energy corresponding to an excessive voltage in correspondence to a current density caused by a power generation at a time of generating a power. Accordingly, in order to keep a temperature for operating the fuel cells to an optimum state, it is necessary to introduce the cooling water to the fuel cells stack so as to remove a generated energy.
In order to secure the gas flow passages and constructing the flow passage for the cooling water, the flow passages for the fuel gas, the oxidizing agent gas and the cooling water are made of a material which is excellent in conductivity, the separator for sealing and separating the respective fluids from each other and the gasket are required for the structure of the fuel cells stack, and a high density carbon or the like is employed for the material of the separator.
In the structure of the conventional fuel cells stack mentioned above, the fuel gas flow passage, the oxidizing agent gas flow passage and the cooling water flow passage are formed by cutting the high density carbon separator. However, since the gas flow passage is complex and it is complex and hard to construct the gas flow passage by cutting the high density carbon, this prevents a cost reduction.
Further, in the fuel cells stack mentioned above, since a plurality of separators, gaskets and fuel cells cells are laminated and constructed, a large number of parts which are necessary in an assembling process of the fuel cells stack is required, a positioning is hard due to a large number of parts, and much labor and time is required, so that this prevent a cost reduction.
As a method of solving the problems mentioned above, there has been disclosed a technique for reducing a cost for processing the separator such as the structure of employing a metal material forming a projection for the separator (Japanese Patent Unexamined Publication No. 8-222237), the structure of the gas flow passage using a porous plate or a corrugated plate (Japanese Patent Unexamined Publication Nos. 8-130023, 6-223836, 6-196177 and 8-203543) and the like.
Further, there has been a technique for reducing a number of the parts such as the structure of integrating the electrode with the gasket (Japanese Patent Unexamined Publication No. 8-45517), the structure of adhering and integrating the gasket with the metal separator (Japanese Patent Unexamined Publication No. 6-196177) and the like.
However, in the conventional techniques mentioned above, it is not possible to sufficiently secure the same gas flow passage as that in the case of processing the high density carbon separator, and further, there is not shown a method of easily constructing the flow passages and reducing the number of the parts.
An object of the present invention is to provide a fuel cells stack which solves the conventional problems mentioned above, constructs a flow passage easily securing a sufficient gas flow passage as well as reducing a number of parts and can reduce a cost.
In order to solve the problems mentioned above, in accordance with the present invention, there is provided a fuel cells stack comprising a plurality of fuel cells each arranging an electrode on both side of a solid electrolyte, separators each constituted by a gas impermeable and dense plate having a conductivity and gaskets laminated to form a plurality of layers, a fuel gas flow passage for supplying a fuel gas to the fuel cell provided on one side surface of the fuel cell, and an oxidizing agent gas flow passage for supplying an oxidizing agent gas to the fuel cell provided on the other side surface, wherein any one of the fuel gas flow passage, the oxidizing agent gas flow passage or a cooling water flow passage used for cooling the fuel cell is provided on the side surface of at least one of the fuel cell and the laminated separator, and the fuel gas flow passage, the oxidizing agent gas flow passage and the cooling water flow passage provided in the separator are constituted by a combination of the gasket integrally formed with the separator and a diffuser formed by a porous body or a corrugated plate made of a material having a conductivity, whereby it is possible to reduce a number of parts and reduce a processing cost of the separator by integrating the separator, various kinds of flow passages and the gasket.
The fuel cells stack in accordance with the present invention is structured such that any one of the fuel gas flow passage, the oxidizing agent gas flow passage or a cooling water flow passage used for cooling the fuel cell is provided on the side surface of at least one of the fuel cell and the laminated separator, and the fuel gas flow passage, the oxidizing agent gas flow passage and the cooling water flow passage provided in the separator are constituted by a combination of the gasket integrally formed with the separator made of a gas impermeable and dense plate having a conductivity and a diffuser formed by a porous body or a corrugated plate made of a material having a conductivity.
The present invention is constructed by simultaneously integrally molding various kinds of flow passages to be formed together with the gasket on the gas impermeable and dense plate having a conductivity corresponding to the separator. However, it is hard to construct the complex various kinds of flow passages only by the gasket. Accordingly, a rough flow passage is constructed at the same time of a construction of the gasket, and a complex flow passage is constructed by combining the diffuser constituted by a porous body made of a material having a conductivity or a corrugated plate in order to supplement this. It is possible to easily construct various kinds of flow passages by attaching the gasket and the porous body made of the material having a conductivity or the corrugated plate to the separator so as to integrally mold. Further, since the structure is integrally molded, a number of the parts is reduced, a positioning can be easily performed in the case of laminating and constructing a stack, a labor and time is reduced, and a cost can be reduced.